I've always thought that if someone has a truly large amount of incriminating information on their computer, it is just better to toss it and get a new one. Hell, I can get a new Dell system for $499. That is a small price to pay every once a year or so, then to risk wondering whether or not some $20 "computer cleaner" got rid of all the incriminating evidence against me on my computer.
I also suggest using a laptop instead of a regular-sized computer. It is much easier to destroy the laptop in case of a raid. Drowning your laptop in water (especially salt water) will completely ruin your computer and make it impossible for LE to read your files. Soda also will work miracles.